In the drilling of oil and/or gas wells, the drill cuttings reach the surface together with the drilling fluid, and they are separated by passage over conventional equipments such as shakers. The drill cuttings can be disposed of by overboard disposal (if off-shore) or by land fill operation if the drilling is on land, less and less frequently as environmental concerns increase. If oil or other hydrocarbons are used in the drilling fluid, the hydrocarbon soaked drill cuttings definitely cannot be thrown overboard because of environmental pollution, and the treatment of hydrocabron-containing drill cuttings is the subject matter of my copending U.S. Pat. application Ser. No. 125,531. Many measures of handling drill cuttings have been proposed, but the only solution used by the drilling industry to date for off-shore drilling is to catch the drill cuttings and by bulk process send the drill cuttings to land for disposal. It is clearly very expensive to send the drill cuttings to land.
U.S. Pat. No. 3,658,654 is directed to apparatus for recovering oil from oil shale and similar solid materials. The oil is removed from solids by a simple pyrolysis process, in the presence of hydrogen to prevent the formation of high molecular weight materials. The oil bearing solids are passed through an elongated substantially horizontal pyrolysis vessel having an auger-type conveyor therein. During passage through the pyrolysis vessel, the oil bearing solids are heated, and the heating means may comprise a furnace or electrical heating coils.
U.S. Pat. No. 4,098,648 discloses a rotatable retort tube having an internal helical member which is fixed to the tube so that no relative rotation is possible. The patent is directed to the solvent extraction of tar sands and oil bearing shale materials, and seeks to overcome a problem regarding the removal of residual solvent from the already substantially oil free materials, before returning the material to the environment. The patent uses a solvent recovery vessel where the solvent is heated and pumped away, and it is unnecessary to raise the temperature much above 200.degree. F. to effect satisfactory evaporation of the solvent. Induction heating is suggested for the heating of the solvent.
U.S. Pat. No. 1,739,066 discloses a device incorporating a counter rotating auger within a rotating drum. The patented device is primarily intended for mixing together particulate materials such as stockfeed, cement, fertilizers, and the like, and discloses that the counter-rotating produces a good mixing effect.
U.S. Pat. No. 4,094,769 discloses an auger/retort system for recovering oil from shale and similar materials. The retort is not rotatable, and may be heated using electrical resistance strip heaters extending longitudinally along the retort. The device is provided with an insulation material which is spaced from and completely surrounds the retort to provide good insulation properties, as well as a safety shield for the strip heaters.
U.S. Pat. Nos. 2,973,312, 3,997,388, and 3,652,447 disclose different methods for heating material in a retort. The first two patents disclose the use of ultrasonic and/or microwave heating, and U.S. Pat. No. 3,652,447 suggests the pyrolytic recovery of oil by the use of pulsed laser beams.
Other patents further illustrating the background of the present invention include U.S. Pat. No. 4,077,868 and U.S. Pat. No. 3,616,266.
U.S. Pat. No. 1,884,379 is directed to a carbonization device wherein a rotating auger is rotated in both a clockwise and a counterclockwise manner by mutilated gears. With the dual direction rotation of the auger, material being treated will be subjected to back and forth movement. U.S. Pat. No. 3,705,285 discloses a track mounted wheeled carrier suitable for the carrying of workpieces from one work station to another. During such transportation the workpiece is effectively heated by an induction heating coil mounted on the wheeled carrier. Thus, during transport the induction heating coil and the material to be heated are stationary with respect to each other.
U.S. Pat. No. 2,722,589 is directed to a device for uniformly heating intermittently moving metallic strip material. The metal strip is intermittently moved into position with a punch or other work device, and the invention of the patent is indicated to lie in moving the strip to be heated and the inductor in a manner relative to each other that during the heating cycle the inductor sees the strip as though it were progressively moving relative thereto.
The problem of removing non-solid materials from aqueous drill cuttings is not as acute as the problem of removing hydrocarbons from drill cuttings, but in many instances the aqueous drill cuttings cannot be simply discharged overboard from an offshore oil well drilling platform, due to environmental regulations, and must be barged back to shore for disposal. Large volumes of drill cuttings are involved and the barging operation tends to be rather expensive. Thus, a need has existed for an apparatus and method to remove the water from the solid drill cuttings, to reduce the volume and/or weight of the solid material which must be barged.